Detached as it may appear, philosophers' thought is influenced by emotions, especially fear of death, especially when it follows the death of parents when they, the children, are still young. Kant's Critiques, which devalue appearances, are affected by the character of his parents, whose uprightness, orderliness, piety, and intractable truth-telling did not prevent their hardships or spare his mother from dying when he was 13. Hume, whose mother died when he was two, conceived his Critique at about the time he underwent a prolonged depression. While Kant became increasingly fearful and hypochondriacal, Hume, believing in psychological causality, grew serene and unafraid of death.